<!DOCTYPE html>
<html>
<head>
<style type="text/css">
.separator {
 height: 20px;
 background-color: green;
}
#parent {
 background-color: lime;
}
#float {
 float: left;
 width: 100px; height: 100px;
 background-color: blue;
}
#clear {
 clear: left;
 margin-top: 40px;
 margin-bottom: 10px;
}
#clear-sibling {
 margin-top: 20px;
 margin-bottom: 30px;
}
</style>
</head>
<body>
<div class="separator"></div>
<div id="parent">
 <div id="float"></div>
 <div id="clear"></div>
 <div id="clear-sibling"></div>
</div>
<div class="separator"></div>
</body>
</html>
